I am in the process of building right now. The house is insulated at 25-30% above code, with additional air-sealing techniques. During the insulation code inspection, the inspector called for the drier waste air vent to be insulated. Is this normal? My builder had never heard of it, but we did it anyway as fighting is more trouble than wrapping some fg around it. We have an unvented attic, if that makes any difference.

I've wondered about this. I'm going to all of this trouble to detail every minute crack and hole in the structure, but between bath vents, dryer vent, and range hood, I've got (3) 4" holes and (1) 6" hole in the envelope. Even if you insulate the pipes, there's still the outside end, which I don't see how to effectively insulate. All of these penetrations are required by code. I know the bath vents could be served with an HRV, but what about the other stuff?

there are better sealing dryer vents (efi.org), and you can use recirculating stove exhausts. bath vents are unnecessary as you say.

I am a big fan of heartland dryer vents. I also like to use them for bath vents- with one exception, I drill a small hole at the base of the vent so any water that accumulates can drain out. I insulate the bath vents, but not the dryer vents- frankly I never thought of it. For long runs in cool spaces this prevents condensation in the ducts. I also use 3- 4” thinwall pvc for bath vents(NOT DRYER vents), with glued seams for long runs. Make sure it has a slight pitch to the outside so any condensate can run out. If you want to do a quick experiment to see why a sealed vent is important, do the following: After the dryer has been off for a day or so, put a thermometer in the dryer and close the door on a cold night. Measure the temp in the dryer- if the vent is leaking, the dryer internal temp will be much closer to the outside temp than you would like. This usually only works in the basement where the stack effect causes a negative pressure. A Hartland dryer vent solves this problem. I am not a fan of recirculating range fans- my forehead is greasy enough already. Cheers, Eric

The logic to insulating the first 10 feet of any metal pipe penetrating the building envelope is that the portion outside draws the heat off a portion of the pipe inside, making it the coolest surface in the house, therefore the area of condensation for in house humidity. If this pipe is in an area where it is not observed, enough moisture can accumulate to cause problems.

The debate about which vents are necessary is bounded by how low your design temperature is. If you are bringing reasonably warm air in on your hrv, it doesn't hurt to send out moist air. On the other hand, if your income air is at -40º, you might not want to send moisture ladened shower air through the exchanger. It will freeze up the core instantly.

See the whole fact that this topic exists on a green house angers me. They have had condenser dryers in the UK for at least the last 10 years. From my understanding none of them even require venting and use a fraction of the electricity. Finally, about a year ago they start talking about releasing them in the US. So, what do they come up with? In January LG, the only company to do this, says they will release one in the US for $1400. Then they go through and list options like a door that opens in two directions and a wireless link to your phone that lets you add custom cycles to it. It is a damn dryer... I dont care what way the door opens, I dont want to post on facebook from it, and I dont want to instagram pictures of me with my clean cloths. I want to throw my cloths in it and have them come out dry. I shouldn't have to pay $1400 for something that is available far cheaper in other parts of the world just so that I am not running a 2000 watt space heater for an hour to dry my cloths.

In short, if your house is really tight try to hold out for a condenser dryer since it shouldnt need any venting and is far more efficient.

FBBP; thanks for your answer; at least it seems to give me a reason that the code, if it does address the issue, exists. I'm glad I provided a forum for the rest of you to address your own issues, however tangential to my question they might be.

I have many issues... seems I figured out more as of late...